DESCRIPTION
DETECT-A-FIRE units are the "heart" of many Fire Protection
Systems. These highly reliable devices have been a standard
of the industry for over 45 years. Many thousands of these
units are now in use controlling the release of extinguishants
such as clean agents, C02, water, or dry chemicals. In some
systems the device is used as an ALARM device, to sense
overheat or fire, and alert personnel. In other systems, it is
used as a RELEASE device, to sense fire and actuate fire
attack systems.
DETECT-A-FIRE units have met with wide acceptance
because they are designed with RATE COMPENSATION. This
provides a unique advantage over both fixed temperature
and rate-of-rise types of detectors because only the
DETECT-A-FIRE unit accurately senses the surrounding air
temperature regardless of the fire growth rate. At precisely
the predetermined danger point, the system is activated.
Fixed temperature detectors must be completely heated to
alarm temperature and therefore a disastrous lag in time may
occur with a fast rate fire. Rate-of-rise devices, on the other
hand, are triggered by the rate of increase in ambient temperature
and are subject to false alarms caused by harmless,
transient thermal gradients such as the rush of warm air from
process ovens.
The outer shell is made of a rapidly expanding alloy which
closely follows changes in surrounding air temperature. The
inner struts are made of a lower expanding alloy. Designed to
resist thermal energy absorption and sealed inside the shell,
the struts follow temperature changes more slowly.
A slow rate fire will heat the shell and struts
together. At the "set point," the unit will trigger, actuating the
alarm or releasing the extinguishant.
A transient rush of warm air up to 40°F/min. may expand
the shell, but not enough to trigger the unit. By ignoring transient
warm air excursions, the DETECT-A-FIRE unit virtually
eliminates false alarms prevalent with
rate-of-rise devices.
If a fast rate fire starts, the shell will expand
rapidly. The struts will close, actuating the alarm or releasing
the agent. The faster the fire rate of growth,the sooner the
DETECT-A-FIRE unit will react.